Treatment of titaniferous ore concentrates to form titanium sulfate



United States Patent TREATMENT OF TITANIFEROUS ORE CONCEN- TRATES TO FORM TITANIUM SULFATE No Drawing. Application August 31, 1951,

Serial No. 244,728

4 Claims. (Cl. 23-117) This invention relates to treatment of ore concentrates. More specifically, it relates to treatment of ore concentrates which have been prepared by flotation methods.

In the preparation of ore materials for processing, it is usually necessary to. remove gangue and other foreign matter from the ore as it is received from the mine before processing into various products of manufacture. It is particularly desirable to remove such materials from titaniferous iron ores inorder to produce useful titanium iron concentrates. These concentrates are used in large tonnages as raw material for the manufacture of various titanium compounds, including titanium tetrachloride and titanium dioxide. During the processing of the concentrate into titanium dioxide, particularly for pigment products, digestion in sulfuric acid is often employed.

Many methods have been utilized for removing the gangue and other foreign matter from the ore to produce ore concentrates. These methods include magnetic separation, wet and dry classifiers, and flotation separation. The present invention relates particularly to the ore concentrates, particularly that of titaniferous material, which has been treated with flotation agents to remove the extraneous materials from titaniferous iron ore. Such titaniferous concentrates are prepared by flotation methods from titaniferous iron ores such as ilmenite and ilmenite-magnetite mixtures. Flotation procedures are used primarily on ore obtained from massive rock deposits instead of titaniferous beach sand materials, since the latter can be concentrated more economically by gravity, magnetic and electrostatic methods. Flotation concentrates prepared from massive rock deposits may possess a wide range of titanium and iron values depending upon the particular ore body employed. However, it has been found that the flotation concentrates obtained from the most widely used titanium ore bodies assay from 30% to 60% TiOz, from to 40% FeO, and from 5% to 25% FezOs. Further, it is known that beach sand materials respond favorably to flotation methods and potential production of flotation concentrates from these materials is indicated.

Flotation methods oftenutilize organic compounds as the flotation agents, particularly oils and organic acids. Among the organic compounds which are often used as flotation agents for preparation of titanium concentrates are crude oil and oleic acid. It has been found that when such organic compounds are employed that such compounds apparently remain with the ore concentrate portion and cannot be removed by normal procedures such as washing. Therefore the organic agents used in flotation concentration procedures for titanium ores are present in the concentrate and also are present in a subsequent sulfuric acid digestion step.

When titanium concentrates which have been treated with such flotation agents are utilized as a raw material for the production of titanium dioxide pigments,.difliculties in operation are encountered, particularly in large scale operation, in the digestion step. Normally the digestion step, that is, dissolving the titanium concentrate in hot sulfuric acid is a rapid and active reaction. This rapid reaction, however, may be controlled and held in check in large scale operations by applying suitable digestion equipment and operational technique well known in the art. However, when a titaniferous iron concentrate which has been treated with flotation agents is reacted with concentrated sulfuric acid, the reaction becomes extremely violentand sometimes approaches explosive magnitude, which is very difficult if not sometimes impossible to control.

Many methods have been tried to alter the sulfuric digestion procedure, when processing a titanium concentrate containing a flotation agent, to overcome the excessive violence of the reaction but none have been successful. It is desirable therefore to provide a method for treating a titanium concentrate containing an organic flotation agent in a manner which will permit the titanium concentrate to be digested in concentrated sulfuric acid in a normal manner. I

An object of this invention therefore is to provide a method for rendering amenable to digestion in concentrated sulfuric acid a titaniferous iron concentrate containing organic flotation agents. Another object is to provide a method for treating a titanium concentrate in a manner which will overcome the violent and uncontrollable digestion reaction in concentrated sulfuric acid. A still further object is to provide an economical method for treatment of a titaniferous material containing an organic flotation agent which will permit a normal digestion procedure to be obtained without affecting the digestion efiiciencies. These and other objects will become apparent from the following more complete description of the instant invention.

Broadly, this invention contemplates treating a titaniferous iron concentrate containing both ferrous and ferric iron and containing an organic flotation agent which comprises subjecting said concentrate to an oxidizing treatment of such a type and for a suflicient length of time that from 2% to 10% of the ferrous iron in the concentrate is converted to ferric iron. It has been found that if the ore concentrate is treated in an oxidizing environment until from 2% to 10% of the ferrous iron in said material is oxidized to ferric iron, the concentrate may be digested in concentrated sulfuric acid in a normal manner. The digestion reaction will proceed in a rapid and active manner but will not produce a violent and uncontrollable digestion reaction. The oxidation of the ferrous iron values is used as a measure to determine the extent of removal of or rendering inactive the flotation agents.

It is believed that the organic flotation agents present in the ore concentrate are either oxidized to an inactive state or are wholly or partially removed during such oxidizing treatment. In any event, the flotation agent during such treatment is rendered incapable of detrimentally affecting the digestion procedure and for all practical purposes may be considered as being substantially removed by such an oxidizing treatment.

The amounts of flotation agents present in the ore concentrate are extremely small. Normally from 1 to 5 lbs. of organic flotation agents are employed per ton of ore in flotation methods. The amount present in the ore concentrate is somewhat lower than the amount employed in the ore flotation method, but usually most of the organic agents remain with the ore concentrate portion. It is difficult to determine the precise percentages of the organic flotation agents present in the ore concentrate by analytical methods because of the small percentages which are used and therefore, it is extremely difficult to determine exactly to what extent the flotation agents may be removed during the oxidation treatment of the present invention.

According to this invention, the extent of oxidizing' treatment which is necessary to obtain a titanium concentrate which may be digested in sulfuric acid in the normal manner may be measured by the amount of oxidation of ferrous iron values in the ore concentrate. It has been established that if from 2% to of the ferrous iron values are oxidized to ferric iron during the oxidation treatement that the ore concentrate con taining the organic flotation agents will be converted to a form which may be digested in sulfuric acid in normal manner. If less than 2% of the ferrous iron values are converted to ferric iron, apparently sufficient organic flotation agent remains in the concentrate in an active form to cause a violent and uncontrollable reaction in the digestion step. If more than 10% of the ferrous iron values are converted to ferric iron, during the oxidizing treatment, the subsequent digestion reaction is somewhat-retarded which results in decreased efficiencies in the digest-ion step. Furthermore, excessive amounts of oxidizing agents must be employed to obtain the additional oxidation which is uneconomical. Furthermore, in processes employing titanium iron solutions, it is most often desirable to reduce substantially all of the ferric iron values to ferrous iron before further processing and therefore, additional and unnecessary amounts of ferric iron present in the concentrate would lead to uneconomical operations in that specific amounts of ferric iron would subsequently have to be reduced to the ferrous state.

Various methods may be employed to oxidize a portion of the ferrous iron to ferric iron. These include heating in the presence of air. In such a procedure the titanium iron concentrate is heated in an oxidizing atmosphere to a temperature from about 250 C. to 500 C. Obviously at the lower temperatures within this range, it is necessary to employ the heat treatment for longer periods of time than that required at the higher temperatures.

Another method for oxidizing a portion of the ferrous iron to ferric iron is to subject the ore to an oxidizing agent such as nitric acid, nitrates, etc. When employing this method for oxidizing the ferrous iron toferric iron, it is convenient to form a slurry of the ore and to add nitric acid to the slurry. In such a slurry it is convenient to employ temperatures from 50 C. to 85 C. and nitric acid or nitrates in amounts from 1.0% to 5.0% based on the weight of the ferrous oxide present in the concentrate. An alternative method which is convenient to employ when adding an oxidizing agent, such as nitric acid or nitrates is to admix the oxidizing agent with the sulfuric acid and to oxidize a portion of the ferrous iron values to ferric iron during the digestion step.

In order to more clearly illustrate the process of the instant invention, the following examples are presented:

Example 1 A titaniferous iron concentrate which had been prepared by treating a ton of titaniferous iron ore with 1.5 lbs. of crude oil and 1.0 lb, of oleic acid in a flotation 100 parts of this concentrate were heated by means of an oil-fired burner with a large excess of air in a rotary ltiln to 430 C. for minutes. The concentrate after 4 suchtreatment was allowed to cool to room temperature and had the following analysis:

Per cent FeO 38.3 F620 3.7 TiO 46.2 Other matter 11.8

Substantially all of the organic flotation agents present in the ore concentrate had been removed. From the analysis before and after the heat treatment it was found that 2.0% of the ferrous iron present in the ore concentrate had been oxidized to the ferric state.

parts of the treated material were digested in 96% sulfuric acid and a rapid and active digestion operation was obtained. In all respects the digestion procedure was carried out in a normal manner. 96.3% of the titanium values in the treated ore concentrate were converted to soluble sulphates during the digestion step.

Example 2 Per cent FeO 38.0 F6203 3.9 TiO2 46.3 Other matter 11.8

Again substantially all of the organic flotation agents present in the concentrate had been removed. From the analysis it was found that 2.8% of the ferrous iron present in the ore concentrate had been oxidized to the ferric state. The dried ore concentrate was digested in concentrated sulfuric acid according to the procedure described in Example 1 and a normal active and rapid reaction was obtained. 96.1% of the titanium values were converted to soluble sulphates during the digestion step.

This procedure has been used with equal success to remove other organic flotation agents such as pine oil, tall oil, cresylic acid, other fatty acids and soaps, and fatty alcohol sulfates.

In order to show that ore concentrates containing organic flotation agents cannot be digested directly in concentrated sulfuric acid without extreme violence, .the following digestion was carried out for comparison purposes. A portion of the ore concentrate described in Example 1 containing the flotation agents which was not treated according to the process of the instant'iin vention was digested directly in concentrated sulfuric acid. Immediately upon admixture with hot sulfuric acid, copious fuming took place and substantially all of the reaction mass foamed and spilled over the top of the reaction vessel. The reaction was extremely violent and could not be held in the reaction vessel. In fact very little of the reaction mass remained in the vessel.

In spite of the small percentage of flotation agent which is present in the titaniferous iron concentrate, a sulfuric acid digestion step is substantially impossible to control unless steps are taken to render the flotation agent inactive before such digestion step.

From the above description and by the examples shown, it has clearly been shown that a titaniferous iron concentrate containing an organic flotation agent when treated according to the process of the instant invention produces a product which may be subsequently digested in sulfuric acid in a normal manner.

It has further been shown that the flotation agent contained in the titaniferous iron concentrate may be either removed substantially or rendered inactive by the treatment process of the instant invention and that after such treatment the concentrate may be digested in concentrated sulfuric acid without extreme violence and explosive characteristics of the digestion reaction. The treatment process is simple and inexpensive to employ.

While this invention has been described and illustrated by the examples shown, it is not intended to be strictly limited thereto, and other modifications and variations may be employed within the scope of the following claims.

We claim:

1. A method for digesting titaniferous iron materials to form titanium sulfate comprising the steps of: subjecting a titaniferous iron material to mechanical ore dressing operations including treatment with an organic flotation agent to form a titaniferous flotation concentrate containing both ferrous and ferric iron values and said organic flotation agent, subjecting said titaniferous flotation concentrate to an oxidizing treatment suflicient to convert from 2% to no more than of said ferrous iron values to ferric iron, thereby to render said organic flotation agent innocuous during digestion of said oxi dized flotation concentrate, adding said oxidized flotation concentrate to concentrated sulfuric acid, and digesting said oxidized flotation concentrate in said sulfuric acid to form titanium sulfate.

2. A method for digesting titaniferous iron materials to form titanium sulfate comprising the steps of: subjecting a titaniferous iron material to mechanical ore dressing operations including treatment with an organic flotation agent to form a titaniferous flotation concentrate containing both ferrous and ferric iron values and said organic flotation agent, heating said titaniferous flotation concentrate in an oxygen containing atmosphere at a temperature in the range of 250-500 C. and for a period of time sufiicient to convert from 2% to no more than 10% of said ferrous values to ferric iron to render said organic flotation agent innocuous during digestion of said oxidized flotation concentrate, adding said oxidized flotation concentrate to concentrated sulfuric acid and digesting said oxidized flotation concentrate in said concentrated sulfuric acid to form titanium sulfate.

3. A method for digesting titaniferous iron materials to form titanium sulfate comprising the steps of: subjecting a titaniferous iron material to mechanical ore dressing operations including treatment with an organic flotation agent to form a titaniferous flotation concentrate containing both ferrous and ferric iron values and said organic flotation agent, subjecting said titaniferous flotation concentrate to treatment by an oxidizing agent selected from the group consisting of nitric acid and nitrates at a temperature in the range of -100 C. and for a period of time sufficient to convert from 2% to no more than 10% of said ferrous iron values to ferric iron to render said organic flotation agent innocuous during digestion of said oxidized flotation concentrate, adding said oxidized flotation concentrate to concentrated sulfuric acid, and digesting said oxidized flotation concentrate in said concentrated sulfuric acid to form titanium sulfate.

4. Method according to claim 3 in which the amount of oxidizing agent is from 1% to 5%, based on the weight of the ferrous iron values present in said titaniferous flotation concentrate.

References Cited in the tile of this patent UNITED STATES PATENTS 2,167,784 Svendsen Aug. 1, 1939 2,183,365 Booge Dec. 12, 1939 2,339,793 Moeklebust et al Jan. 25, 1944 2,339,808 Ravnestad et al Jan. 25, 1944 2,403,248 Todd July 2, 1946 2,429,209 Mayer Oct. 21, 1947 2,631,941 Cole Mar. 17, 1953 FOREIGN PATENTS 10,062 Great Britain Apr. 25, 1891 of 1890 

1. A METHOD FOR DIGESTING TITANIFEROUS ION MATERIALS TO FORM TITANIUM SULFATE COMPRISING THE STEPS OF: SUBJECTING A TITANIFEROUS IRON MATERIAL TO MECHANCIAL ORE DRESSING OPERATIONS INCLUDING TREATMENT WITH AN ORGANIC FLOTATION AGENT TO FORM A TITANIFEROUS FLOTATION CONCENTRATE CONTAINING BOTH FERROUS AND FERRIC IRON VALUES AND SAID ORGANIC FLOTATION AGENT, SUBJECTING SAID TITANIFEROUS FLOTATION CONCENTRATE TO AN OXIDIZING TREATMENT SUFFICIENT TO CONVERT FROM 2% TO NO MORE THAN 10% OF SAID FERROUS IRON VALUES TO FERRIC IRON, THEREBY TO RENDER SAID ORGANIC FLOTATION AGENT INNOCUOUS DURING DIGESTION OF SAID OXIDIZED FLOTATION CONCENTRATE, ADDING SAID OXIDIZED FLOTATION CONCENTRATE TO CONCENTRATE SULFURIC ACID, AND DIGESTING SAID OXIDIZED FLOTATION CONCENTRATE IN SAID SUFLURIC ACID TO FORM TITANIUM SULFATE. 